The present invention relates to a liquid crystal display employed in color liquid crystal displays, color video cameras, image scanners, personal computers, and the like, and a color filter, and a production method of the same.
In recent years, along with the rapid growth of portable personal computers, demand for liquid crystal displays has tended to increase, and at the same time, cost reduction of such devices has been demanded. Especially, cost reduction for expensive color filters has increasingly been demanded. Namely, desired are excellent quality color filters, which are produced at high yield, employing a short production process, and said production method thereof. However, those, which meet with requirements, have not yet been realized.
Color filters for liquid crystal display s are prepared by suitably arranging three filters of blue (B), green (G), and red (R) color. one color filter forms each pixel, and the cell size formed by one pixel is approximately (60 to 100 xcexcm)xc3x97(180 to 300 xcexcm). In order to minimize surface reflection, each pixel cell is surrounded by a partition wall, that is, a black matrix (hereinafter referred to as BM).
Said color filter is a simple structure. However, due to its complicated and lengthy production process, the yield is low which increases the cost. Thus, demanded are high quality color filters having reduced production cost.
The conventional production methods will now be described below.
The first production method of the color filter for liquid crystal display, which is most frequently employed, is a dyeing method.
In said method, a dyeable photosensitive polymer layer is formed on a support substrate. With the use of photolithography, patterning is carried out while matching the filter shape, and the resulting pattern is dyed.
This operation is repeated three times, one for each color, and subsequently a protective layer is provided. Thus a filter, having three colors of B, G, and R is formed.
The second method is a pigment dispersion method. In said method, a photosensitive resinous layer, into which pigments are dispersed, is formed on a support substrate. The resulting layer is subjected to patterning to obtain a monochromatic pattern.
This operation is also repeated three times, once for each color, and subsequently a protective layer is provided. Thus a filter, having three colors of B, G, and R, is formed.
The third method is an electrodeposition method. In this method, a filter pattern is formed on a support substrate, employing an electrode. Subsequently, the resulting support substrate is immersed into an electrodeposition coating composition comprising pigments, resins, and solvents, and a first color is electrodeposited by applying electricity to the electrode. Said operation is again repeated three times, once for each color, and subsequently a protective layer is provided. Thus a filter having three colors of B, G, and R is formed.
The fourth method is a printing method. In this method, pigments are dispersed into a thermohardening resin and printing is carried out on a glass support substrate. Again, said operation is repeated three times, once for each color, and subsequently a protective layer is provided. Thus a filter, having three colors of B, G, and R is formed.
Drawbacks common with conventional methods are as follows. In order to produce three colors of B, G, and R, it is necessary to repeat the process three times, such as spin coating of photosensitive resins, exposure, development, electrodeposition, printing, and the like. Thus, a lot of resources are wasted; due to the lengthy process, staining chances increase; the yield decreases and the cost increases.
Further, since in the electrodeposition method, dyes are deposited on the electrode, it is necessary to electrically connect an electrode pattern. Thus the pattern shape of filters is limited and at present, it is difficult to apply this method to the TFT use.
Still further, in the printing method, for example, in offset printing, ink is transferred twice and the resolution is degraded, and it is difficult to obtain a finely spaced pattern. Further, since the filter surface results in unevenness, a subsequent process to flatten the surface is required.
In order to overcome these drawbacks, color filters, which are prepared employing an ink jet method, are proposed.
This ink jet method is different from conventional methods and is a method in which each of R, G, and B inks is ejected onto a support substrate from the respective nozzles to form a colored layer. When this method is employed, the required amount of ink can be applied onto a required place at a specific time. Accordingly, there is no waste of ink. Further, since colored layers of R, G, and B are formed simultaneously, the production process is shortened, and it is possible to markedly reduce cost.
However, when a colored layer is formed by ejecting ink onto a pixel forming area (hereinafter occasionally referred to as a convex section) which is formed on the support substrate, employing said ink jet method, the support substrate, which is different from cloth and paper, does not absorb ink. As a result, the ink floods from one pixel (one concave section), and tends to mix with the ink in the adjacent pixel (the concave section).
Further, when physical parameters, such as surface tension, viscosity, and the like of the employed ink, are not adaptable to the surface free energy of the support substrate, the colored layer is repelled. As a result, the thickness of the filter layer loses its uniformity and the color density also tends to not be uniform and white spot marks or ink-omitted spots, where an ink could not be applied due to some defects, tend to form. Further, the surface of the colored layer tends to be roughened, and problems occur in which the layer is incapable of being brought into uniform contact with the liquid crystal layer.
Since the ink jet method is highly efficient and minimizes material waste compared to the conventional methods, it is possible to produce color filters at low cost. However, as described above, the ink in the concave sections tends to mix with that in adjacent concave sections and the ink density (the ink concentration) in the concave sections loses its uniformity. Particularly, big problems occur in which white spot marks tend to form due to lack of ink in parts of concave sections or in the boundary between the concave and convex sections.
In order to overcome the stated drawbacks, it is desirous that the ink, which is ejected onto one of concave sections, does not flow into adjacent concave sections while spreading across the surface of the black matrix area (hereinafter occasionally referred to as the convex section) so that the ink in one concave section does not mix with that in adjacent concave sections.
Further, it is desirous that the ink in the concave sections spreads uniformly.
In order to overcome the stated drawbacks, the surface of the support substrate is treated so that the convex section is ink-repellent while the concave section is ink-affinitive. However, the concave section, having ink affinity, is surrounded by the convex sections having ink repellency. As a result, even though ink spreads uniformly in the concave section, the ink is repelled in the area in contact with the convex section. Thus problems occur in which the color density at the periphery of the concave section decreases, and the contrast of displayed color images is degraded due to the tendency of formation of white spot marks.
As noted above, in order to manufacture filters employing the ink jet method, the treatment that a support substrate (a glass substrate) is treated in order to be accurately and minutely divided into ink-repellent areas and ink-affinitive areas, has been conducted in many prior arts.
For example, Japanese Patent Publication Open to Public Inspection Nos. 9-230123, 7-35916, and 4-123005 disclose methods to form color filters as follows. A photosensitive material and a material such as fluorine-contained resins and silicone-contained resins, which is capable of forming a low energy surface, are multilayered onto a support substrate, and the coating is subjected to irradiation of ultraviolet rays through a pattern matching concave sections or convex sections, and developed to remove the fluorine-contained resins or silicone-contained resins from the concave sections while remaining those in convex sections, onto which ink is ejected to form said color filters.
Since in said method, a photolithographic technique is employed, it is possible to correctly provide ink affinity and ink repellency to each of the concave sections and convex sections. However, dye density tends to decrease due to ink repellency at the boundary between the concave section and the convex section, and the contrast of displayed images tends to decrease due to the formation of white spot marks.
Further, since the glass surface of the concave section has high surface free energy, ink affinity is excellent. However, fluorine or silicone-contained materials having low surface energy tend to be adsorbed onto the surface of the concave section, and thus ink affinity in the concave section tends to be lost.
Due to that, it is necessary to remove applied materials by etching the glass surface in the concave section, using hydrofluoric acid, lasers, and the like.
Further, when fluorine-contained resins, as well as silicone-contained resins, exist in the convex section, it is impossible to apply the protective layer due to their repellency. Therefore, it is necessary to remove them. Then, the process becomes markedly complex due to the additional steps.
There are methods other than this which can be considered. For example, Japanese Patent Publication Open to Public Inspection Nos. 8-201615, 8-227012, 8-230314, and others disclose a method in which a photosensitive resin is applied onto a support substrate; the resulting coating is subjected to irradiation of ultraviolet rays through a mask which is adjusted to the shape of the convex or concave sections; and mixing of ink between concave sections is minimized utilizing the difference in ink absorbability between the irradiated area and the non-irradiated area. However, it is impossible to provide sufficient difference in ink absorbability due to the presence and non-presence of irradiation and it is also impossible to sufficiently minimize ink mixing. Further, since the ink absorptive layer is provided, a decrease in resolution, as well as an increase in production cost, is caused. This method also includes a markedly complex process due to the many additional steps.
In order to minimize the decrease in ink density and white spot marks in the boundary between the convex sections and the concave sections, several methods are disclosed. For example, Japanese Patent Publication Open to Public Inspection No. 9-127327 discloses a method in which the ink repellency on the side surface of convex sections is slightly lowered.
Still further, Japanese Patent Publication Open to Public Inspection No. 9-258208 discloses a method in which the convex section is comprised of double layers, in which the ink repellency of the lower layer is lower than the upper layer.
In these methods, photopolymers are employed in combination with fluorine-contained compounds. Accordingly, a plurality of processes, which are longthy and complex, are required. Thus these methods are not economically advantageous and also result in waste of resources.
In a method described in Japanese Patent Publication Open to Public Inspection No. 10-115703, color unevenness, as well as lack of color, is minimized by flattening the meniscus shape by decreasing the contact angle at the boundary area by controlling the receding contact angle of the ink droplet to the convex section at no more than 50 degrees. However, the receding contact angle of no more than 50 degrees is not preferred because it is impossible to sufficiently flatten the meniscus due to the high contact angle.
In another method described in Japanese Patent Publication Open to Public Inspection No. 9-329706, the lower portion of a convex section is formed employing hydrophilic silicon oxide while the upper portion of the same is formed employing amorphous silicon having hydrophobicity. This method is not preferred because an expensive apparatus, such as a plasma CVD, is required.
As noted above, when high precision color filters are produced employing the ink jet method, a major challenge is the development of a technique in which a support substrate is treated so that the concave section exhibits ink affinity and the convex section exhibits ink repellency, and further the boundary of the concave section with the convex section does not exhibit marked difference in wettability.
Support substrates for the color filter are preferably prepared by applying resins mixed with carbon black onto a glass surface and by forming convex sections thereon.
Concave sections are preferably formed, for example, on a glass surface. The glass surface has high surface free energy. Accordingly, when adsorbed materials having low surface energy are removed, the glass surface exhibits sufficient wettability without need of special ink affinity treatment.
However, since convex sections are formed employing resins which generally exhibit, for example, a medium range of surface free energy, it is impossible to prevent the convex sectionspreading across movement of a solvent-based ink having especially low surface free energy. Therefore, it is preferably proposed that convex sections are treated with fluorine and silicon compounds which provide low surface free energy so that the convex sections exhibit ink repellency.
Conventional methods utilize a photolithographic technique. Accordingly, it is possible to accurately provide ink-repellent treatment onto the surface of convex sections. However, ink repellency due to marked difference in wettability resulted in the boundary line of the convex sections with the concave sections is not sufficiently minimized.
Further, said photolithographic technique exhibits problems in which various processes such as spin coating, exposure, development, removal of materials adsorbed in concave sections, removal of surface treatment materials, and the like, are required, with a resultant increase in cost.
An object of the present invention is to overcome a problem in conventional methods, in which it is impossible to efficiently minimize ink repellency which results at the boundary line between convex sections and concave sections.
In the present invention, by treating a support substrate employing an extremely simple method, it is possible to minimize ink-spreading across convex sections, to uniformly spread an ink in a concave section, and to minimize ink repellency which results at the boundary line between the concave sections and the convex sections.
Namely, it is an object of the present invention to provide a problem-free color filter having a uniform color density of ink-tinted layers for liquid crystal displays for color liquid displays, color video cameras, image scanners, personal computers, and the like, and a method to prepare less expensive color filters at higher productivity.
The object of the present invention is achieved employing the following embodiments.
(1-1) A method of manufacturing a color filter having a substrate comprising black matrix sections and image forming sections, comprises:
a step of applying a treatment onto the substrate so as to provide influence to a contact angle between an ink meniscus and the black matrix sections before applying an ink onto the substrate.
(1-2) In the method of (1-1), the treatment is a process to change the contact angle with elapse of time.
(1-3) In the method of (1-2), the method further comprises:
a step of applying an ink onto the image forming sections after the step of applying the treatment.
(1-4) In the method of (1-2), the treatment is a surface treatment employing chemical composition.
(1-5) In the method of (1-2), the treatment is a treatment to lower the contact angle.
(1-6) In the method of (1-2), each of the image forming sections is assigned respectively with a corresponding ink to be applied thereon, the method further comprises:
a step of applying the corresponding ink respectively onto each of the image forming sections.
(1-7) A method of manufacturing a color filter having a substrate comprising black matrix sections and image forming sections, wherein each of the image forming sections is assigned respectively with a corresponding ink to be applied thereon, comprises steps of:
applying a surface treatment onto the substrate with chemical composition which is substantially soluble in an ink; and
applying the corresponding ink respectively onto each of the image forming sections.
(1-8) In the method of (1-7), the surface treatment is applied onto both of the black matrix sections and the image forming sections.
(1-9) In the method of (1-4), the chemical composition is a surface active agent.
(1-10) In the method of (1-6), the chemical composition is a surface active agent.
(1-11) In the method of (1-7), the chemical composition is a surface active agent.
(1-12) In the method of (1-9), at least two types of surface active agents each having a perfluoro group are employed as the surface active agent.
(1-13) In the method of (1-10), at least two types of surface active agents each having a perfluoro group are employed as the surface active agent.
(1-14) In the method of (1-11), at least two types of surface active agents each having a perfluoro group are employed as the surface active agent.
(1-15) In the method of (1-9), a surface active agent which is substantially soluble in an ink and a surface active agent which is substantially insoluble in an ink are employed as the surface active agent.
(1-16) In the method of (1-10), a surface active agent which is substantially soluble in an ink and a surface active agent which is substantially insoluble in an ink are employed as the surface active agent.
(1-17) In the method of (1-11), a surface active agent which is substantially soluble in an ink and a surface active agent which is substantially insoluble in an ink are employed as the surface active agent.
(1-18) In the method of (1-15), a surface active agent which is substantially soluble in a solvent of an ink and a surface active agent which is substantially insoluble in a solvent of an ink are employed as the surface active agent.
(1-19) In the method of (1-16), a surface active agent which is substantially soluble in a solvent of an ink and a surface active agent which is substantially insoluble in a solvent of an ink are employed as the surface active agent.
(1-20) In the method of (1-17), a surface active agent which is substantially soluble in a solvent of an ink and a surface active agent which is substantially insoluble in a solvent of an ink are employed as the surface active agent.
(1-21) A method of manufacturing a color filter having a substrate comprising black matrix sections and image forming sections, wherein each of the image forming sections is assigned respectively with a corresponding ink to be applied thereon, comprises steps of:
applying the corresponding ink respectively onto each of the image forming sections, wherein at 30 seconds after applying the ink, an advancing contact angle of the ink on the black matrix sections is not larger than 90xc2x0 and a receding contact angle of the ink on the black matrix sections is not larger than 40xc2x0, and wherein with elapse of time under normal ambient temperature and normal atmospheric pressure, the advancing contact angle is lowered to be not larger than 30xc2x0 and the receding contact angle is lowered to be not larger than 15xc2x0.
(1-22) A method of manufacturing a color filter having a substrate comprising black matrix sections and image forming sections, wherein each of the image forming sections is assigned respectively with a corresponding ink to be applied thereon, comprises steps of:
applying the corresponding ink respectively onto each of the image forming sections,
wherein immediately after applying the ink, an advancing contact angle of the ink on the black matrix sections is larger than an advancing contact angle of the ink on the image forming sections,
wherein with elapse of time, the advancing contact angle of the ink on the black matrix sections is lowered, and
wherein within 2 minutes after applying the ink, the advancing contact angle of the ink on the black matrix sections is lowered to be not larger than an angle larger 10xc2x0 than the advancing contact angle of the ink on the image forming sections.
(1-23) A method of manufacturing a color filter having a substrate comprising black matrix sections and image forming sections, comprises steps of:
a step of applying a treatment onto the substrate such that, immediately after applying the ink, an advancing contact angle of the ink on the black matrix sections is larger than an advancing contact angle of the ink on the image forming sections,
wherein with elapse of time, the advancing contact angle of the ink on the black matrix sections is lowered, and
wherein within 2 minutes after applying the ink, the advancing contact angle of the ink on the black matrix sections is lowered to be not larger than an angle larger 10xc2x0 than the advancing contact angle of the ink on the image forming sections.
(1-24) In the method of (1-21), a surface active agent which is substantially soluble in a solvent of an ink and a surface active agent which is substantially insoluble in a solvent of an ink are employed as the surface active agent.
(1-25) In the method of (1-22), a surface active agent which is substantially soluble in a solvent of an ink and a surface active agent which is substantially insoluble in a solvent of an ink are employed as the surface active agent.
(1-26) In the method of (1-23), a surface active agent which is substantially soluble in a solvent of an ink and a surface active agent which is substantially insoluble in a solvent of an ink are employed as the surface active agent.
(1-27) In the method of (1-24), at least two types of surface active agents each having a perfluoro group are employed as the surface active agent.
(1-28) In the method of (1-25), at least two types of surface active agents each having a perfluoro group are employed as the surface active agent.
(1-29) In the method of (1-26), at least two types of surface active agents each having a perfluoro group are employed as the surface active agent.
(1-30) In the method of (1-3), in the step of applying the ink, the ink is applied by an ink-jet method.
(1-31) In the method of (1-7), in the step of applying the ink, the ink is applied by an ink-jet method.
(1-32) In the method of (1-21), in the step of applying the ink, the ink is applied by an ink-jet method.
(1-33) In the method of (1-22), in the step of applying the ink, the ink is applied by an ink-jet method.
(1-34) In the method of (1-23), in the step of applying the ink, the ink is applied by an ink-jet method.
(1-35) A color filter, manufactured by the method of (1-30).
(1-36) A color filter, manufactured by the method of (1-31).
(1-37) A color filter, manufactured by the method of (1-32).
(1-38) A color filter, manufactured by the method of (1-33).
(1-39) A color filter, manufactured by the method of (1-34).
(1-40) A liquid crystal display, comprises a color filter manufactured by the method of (1-30).
(1-41) A liquid crystal display, comprises a color filter manufactured by the method of (1-31).
(1-42) A liquid crystal display, comprises a color filter manufactured by the method of (1-32).
(1-43) A liquid crystal display, comprises a color filter manufactured by the method of (1-33).
(1-44) A liquid crystal display, comprises a color filter manufactured by the method of (1-34).
(1-45) A liquid crystal display, comprises a color filter manufactured by the method of (1-35).
Further, the above object may be attained by the following preferable embodiments.
(2-1) A production method of a color filter wherein prior to ink application, treatment is carried out, which affects the contact angle between the convex section of a support substrate for a color filter, having convex sections as well as concave sections and the ink meniscus, and varies said contact angle with time.
(2-2) The production method of a color filter described in
(2-1), wherein the treatment, which affects the contact angle between said convex section and said ink meniscus, and varies said contact angle with time, is a surface treatment employing chemical compounds.
(2-3) The production method of a color filter described in
(2-1), wherein the treatment, which affects the contact angle between said convex section and said ink meniscus, and varies said contact angle with time, is a treatment which lowers said contact angle.
(2-4) A production method of a color filter wherein a support substrate for a color filter, having convex sections as well as concave sections, is subjected to surface treatment employing a chemical compound which affects the contact angle between the convex section and the ink meniscus.
(2-5) A production method of a color filter wherein a support substrate for a color filter is subjected to surface treatment employing a chemical compound which is substantially ink-soluble, and said ink which corresponds to each pixel forming area is applied.
(2-6) The production method of a color filter described in (2-2), (2-4), or (2-5), wherein a chemical compound, which is employed to carry out surface treatment which affects the contact angle between the convex section of a support substrate for a color filter, having convex sections as well as concave sections and the ink meniscus, is a surface active agent.
(2-7) The production method of a color filter described in (2-6), wherein at least two types of surface active agents, having a perfluoro alkyl group, are employed in combination.
(2-8) The production method of a color filter described in (2-6) or (2-7), wherein a support substrate for said color filter is subjected to surface treatment employing a surface active agent which is substantially soluble in an ink droplet, together with a surface active agent which is substantially insoluble in said ink.
(2-9) The production method of a color filter described in (2-8) wherein a support substrate for said color filter is subjected to surface treatment employing a surface active agent which is substantially soluble in a solvent of an ink droplet together with a surface active agent which is substantially insoluble in said solvent of said ink.
(2-10) The production method of a color filter described in (2-9) wherein said surface treatment is carried out so that the ratio of the employed amount of said substantially soluble surface active agent to said substantially insoluble surface active agent is in the range of 1,000:1 to 1:1.
(2-11) The production method of a color filter described in 10. wherein said surface treatment is carried out so that the ratio of the employed amount of said substantially soluble surface active agent to said substantially insoluble surface active agent is in the range of 500:1 to 5:1.
(2-12) In a production method of a color filter of applying an ink onto a support substrate for said color filter, which has convex sections as well as concave sections, a production method of said color filter wherein immediately after ink droplet application (30 seconds after the application of an ink droplet), the advancing contact angle of an ink droplet to the convex section of the support substrate of said color filter is no more than 90 degrees and the receding contact angle of the same is no more than 40 degrees, and after an elapse of time (after 2 minutes at normal temperature and pressure), the advancing contact angle decreases to no more than 30 degrees and the receding contact angle of the same decreases to no more than 15 degrees.
(2-13) In a production method of a color filter of applying an ink onto a support substrate for said color filter, which has convex sections and pixel forming areas, a production method of a color filter wherein the advancing contact angle of an ink droplet to the convex section of the support substrate of said color filter is no more than 90 degrees immediately after ink droplet application (30 seconds after the application of an ink droplet) and the receding contact angle of the same is no more than 40 degrees, and the advancing contact angle after an elapse of time (after 2 minutes at normal temperature and pressure) decreases to no more than 30 degrees and the receding contact angle of the same decreases to no more than 15 degrees.
(2-14) A production method of a color filter wherein the advancing contact angle of an ink droplet to the convex section of a support substrate for said color filter, which has convex sections as well as concave sections is, immediately after ink application, greater than the advancing contact angle of said ink droplet to the surface of said support substrate of pixel forming areas to which said ink is to be applied, decreases with an elapse of time, and within 2 minutes after ink application, decreases to a value or less, which is 10 degrees larger than the advancing contact angle of said ink droplet to the support substrate of said pixel areas.
(2-15) A production method of a color filter wherein said support substrate of a color filter is subjected to surface treatment so that the advancing contact angle of an ink droplet to the convex section of a support substrate for said color filter, which has convex sections as well as concave sections is, immediately after ink application, greater than the advancing contact angle of said ink droplet to the surface of said support substrate of pixel forming areas to which said ink is to be applied, decreases with an elapse of time, and within 2 minutes after ink application, decreases to a value or less, which is 10 degrees larger than the advancing contact angle of said ink droplet to the support substrate of said pixel areas.
(2-16) The production method of a color filter described in any one of (2-12) through (2-15) wherein a support substrate for a color filter is subjected to surface treatment employing a surface active agent which is substantially soluble in an organic solvent in an ink, as well as a surface active agent which is substantially insoluble in said organic solvent in the same.
(2-17) The production method of a color filter wherein a support substrate for said color filter is subjected to surface treatment employing at least two types of surface active agents, both having a perfluoroalkyl group.
(2-18) The production method of a color filter described in any one of (2-1) through (2-17), comprising a coloration process employing an ink jet method.
(2-19) When a color filter, which is characterized in being produced employing the production method described in any one of (2-1) through (2-18), is applied to a liquid crystal display, it is possible to obtain markedly improved images. Further, no image problems occur due to use of said color filter and the resulting unit provides excellent performance.